Casters are employed to facilitate the movement of heavy articles such as cargo within an airplane. The cargo casters in such an application contain rollers, or wheels, that provide a roller plane above the main cargo deck, along which the cargo travels. Such cargo casters significantly lessen the burden of loading and unloading the cargo.
Current cargo caster assemblies consist of a base, a ball bearing assembly, and a roller assembly. The base is mounted, either directly or indirectly, to the main cargo deck at appropriate positions. The ball bearing assembly is a pre-packaged unit, containing a ring of ball bearings captured between an inner race and an outer race that allows the races to freely move relative to each other. The ball bearing assembly is of circular design, such that its outer race is secured to an appropriately sized circular recess in the base. Its inner race is secured to the circular frame of the roller assembly, which includes rollers, or wheels, that are freely rotatable and have a contacting surface that creates a roller plane above the cargo caster assembly. Because the roller assembly is coupled to the base by the ball bearing assembly, the rollers are not only free to rotate, but their orientation may be changed by a full three hundred sixty degrees. This full range of orientation feature is required due to the various angles at which cargo must be moved during the loading and unloading process.
Current cargo caster assemblies allow dust and other contaminants to reach the bearing surfaces, thereby increasing the bearing resistance which impedes the free rotation of the roller assembly relative to the base. This directly translates to increased efforts required to move the cargo during loading and unloading. Currently, the only recourse to this accumulation of dust and other contaminants is to frequently replace the ball bearing assembly, or to attempt to clean the contaminants from the bearing surfaces. The latter process has not been successful in the past since the contaminants remain trapped within the materials used to lubricate the bearing surfaces.
The current design has also resulted in a ball bearing assembly that has not remained adequately secured to the base and the roller assembly. When the ball bearing assembly separates from either, the change of roller orientation feature is lost.
Because current ball bearing assemblies consist of steel ball bearings captured by steel inner and outer races, they are of significant weight. Given that hundreds of cargo caster assemblies are used in a single cargo airplane, their weight is of grave concern and it directly diminishes the amount of cargo that may safely be carried.
Ball bearing assemblies of steel construction are expensive to produce, and therefore current cargo caster assemblies utilizing them are similarly expensive to produce. Because the ball bearing assemblies currently being used frequently must be replaced due to fouling or separating, the repair and maintenance costs of current cargo caster assembles is also prohibitive.
The problems detailed above are not unique to cargo caster assembles, but are found in virtually any environment having two parts with an interfacing ball bearing requirement. Accordingly, there has been a long-felt need for a bearing assembly that is relatively inexpensive to produce and maintain, that significantly reduces fouling of the bearing surfaces by dust and other contaminants, and that, with respect to cargo caster assemblies, is of reduced weight and attaches to existing mounts. This invention is directed to satisfying this need.